c-strtod, c-strtold: Use the bug fixes for strtod, strtold. * lib/stdlib.in.h (GNULIB_defined_strtod_function, GNULIB_defined_strtold_function): New macros. * lib/c-strtod.c (HAVE_GOOD_STRTOD_L): New macro. (STRTOD): Ignore HAVE_C99_STRTOLD. (c_locale): Don't define it on platforms where strtod_l/strtold_l is deemed buggy. But do use it on platforms where uselocale exists and is usable. (C_STRTOD): Don't use STRTOD_L on platforms where strtod_l/strtold_l is deemed buggy. On platforms where uselocale exists and is usable, use uselocale and strtod/strtold. * m4/c-strtod.m4 (gl_C99_STRTOLD): Remove macro. (gl_C_STRTOD): Require gt_FUNC_USELOCALE. (gl_C_STRTOLD): Likewise. Define HAVE_C99_STRTOLD unconditionally. * modules/c-strtod (Files): Add m4/intl-thread-locale.m4. (Depends-on): Add strtod. * modules/c-strtold (Files): Add m4/intl-thread-locale.m4. (Depends-on): Add strtold.